A fiber-reinforced composite material in which carbon fibers, aramid fibers, glass fibers or the like are used as reinforcing fibers has been widely utilized for structural materials of aircrafts, vehicles or the like, or in general industries and sports such as a tennis racket, a golf club shaft and a fishing rod by utilizing high specific strength and high specific elasticity thereof.
For example, Patent Document 1 describes a stamping molding material molded obtained by heating and pressurizing a composite laminate made from a glass fiber sheet body containing a thermoplastic resin to mold the composite laminate in a sheet form, and a method for manufacturing the stamping molding material. According to Patent Document 1, although a stereoscopic product can be manufactured by an integral molding method in a short tact time, since it is difficult to control fiber orientation due to fluidity, it is difficult to obtain a shaped product which is thermally and mechanically isotropic and has less warpage attributed to differential shrinkage caused by orientation.
Patent Document 2 describes a layered base material which is made of a prepreg base material including unidirectionally oriented reinforcing fibers and a thermoplastic resin and has some portions with different layer thicknesses.
However, in order for the layered base material to be thermally and mechanically isotropic, a plurality of prepreg base materials need to be layered such that the reinforcing fibers are isotropically placed, and there are many limitations in preparing base materials, performing a molding process, and designing a product.
In the injection molding field, since a reinforcing fiber may be cut or broken by a screw during an injection molding process, it is difficult to obtain a shaped product made of a fiber-reinforced composite material including a reinforcing fiber with a long fiber length. Accordingly, development of a shaped product which is made of a fiber-reinforced composite material using a reinforcing fiber with a fiber length of 1 mm or less has been carried out. However, since such a shaped product includes the reinforcing fiber with a short fiber length, a mechanical property, or the like, is not sufficient. Further, this shaped product has a problem that the reinforcing fiber is oriented in a flow direction of a molten resin during a molding process, so that a physical property tends to be anisotropic.
Thus, a shaped product, which includes a reinforcing fiber with a long fiber length and a thermoplastic resin, has an isotropic property, and is made of a fiber-reinforced composite material having an excellent physical property, has not been developed sufficiently. In particular, a shaped product having a standing plane inclined at about 90 degrees with respect to a reference plane, a shaped product having an extremely small corner R (curvature) between a reference plane and a standing plane, a shaped product having a thin-walled standing plane, and a shaped product having an extremely deep standing plane, which are made of an isotropic fiber-reinforced composite material and have a physical property endurable to practical use, have not been achieved.